When you are the only rice mill for an entire country, one broken aluminum can on the packaging line bringing the whole operation to a standstill is a big deal. Dainty, Canada’s sole rice mill, uses heat and pressure to process imported rice, which means there is plenty of potential for broken cans.
Dainty Rice has been a Canadian staple since the 1880s, but a lot has changed since the company processed its first 1,700-ton rice shipment from Myanmar in Montreal. The rice milling facility moved to Windsor, Ont., in 1967, and the company has continued to focus on its mission of delivering easy-to-use rice products for families even as it has grown tremendously.
One thing that has not changed is the importance of the brand selling cooked rice in a can. It has become an iconic symbol of the company since rolling off post-war production lines in 1947.
Preventing waste and downtime
The significance of the can for Dainty’s brand and mission is just one reason why they contacted Southpoint Automation of Leamington, Ontario, for assistance in developing and installing an inspection system for incoming blank cans.
“One damaged rim on a can will stop the entire canning process,” explains Jeremy Atkinson, co-owner and automation specialist at Southpoint. “Damaged cans in the broiler can lead to a serious mess. This project was to prevent waste and downtime in the canning room.”
Southpoint is a full-service automation integrator for robots, manufacturing, and remote monitoring solutions for the automotive, packaging, and related markets. To automate Dainty’s critical can inspection step, Atkinson enlisted the help of machine vision experts at Shelley Automation of Windsor.
Automating aluminum can inspection with In-Sight
Prior to the automated solution, Dainty employees manually inspected can blanks. However, manual inspectors missed many defective cans, which slowed the entire process. A feasibility study conducted by Shelley revealed that with a conveyor speed of 350 millimeters per second, Dainty needed a vision system that could operate with exposure times of 0.25 milliseconds or less to eliminate blur, and could inspect for shape and edge defects at a rate of 200 milliseconds per can.
Working with this application data, Atkinson chose a Cognex In-Sight 7800 vision system. “We initially looked at the 7600 camera, which has the same 640 x 480 resolution, but the 7800 comes with a more powerful processor, which allowed us to meet the 200-millisecond-per-inspection requirement,” he says.
Atkinson paired the In-Sight 7800 with a diffuse light panel (DLP) red light with a through-hole for mounting the camera and a matching red band-pass filter to limit the camera to red light reflecting off the tops of cans. With the camera and light aligned along the same axis using the through-hole, and with a diffuse light source to reduce hot spots (spots of high reflection from cans’ polished metal surfaces), the system was able to repeatedly generate high-quality images of cans as they passed through the inspection station (see figure).
Initially, Atkinson tried the inspection system using the In-Sight edge tool algorithm. However, Cognex suggested its bead tool as a faster and more robust approach. The bead tool draws connecting circles around an edge to evaluate continuity (that is, to find breaks) and to determine the arc angle as part of a roundness analysis of a can’s top edge.
Results are stored locally in the In-Sight 7800’s internal memory, but Atkinson says there is interest in passing the information back to the plant’s enterprise resource planning system.
The support given by Southpoint Automation is an enormous positive, plus there’s been zero maintenance issues with the equipment after being installed, says the Dainty Rice team automation team.